Evaluation of nitrate tolerance in patients with coronary heart disease by vascular ultrasonography and treadmill exercise

The aim of this study was to evaluate nitrate tolerance in patients with coronary heart diseases by vascular ultrasonography and treadmill exercise. According to the dosage interval of isosorbide dinitrate, 66 patients with coronary heart disease were divided into group A and group B in a random, control and double-blind method. Isosorbide dinitrate was given every 6 hours in group A and every 12 hours in group B for one week. Before and after the therapeutic period, the diameters of brachial arteries were measured by vascular ultrasonography at baseline and 5 min after sublingual administration of 10 mg isosorbide dinitrate, and the treadmill exercise test was performed in all subjects. The results showed that diameters of brachial arteries were increased significantly after sublingual isosorbide dinitrate in both groups before the therapeutic period. After the therapeutic period, dilation of brachial arteries induced by sublingual isosorbide dinitrate was more marked in group B than in group A. Compared with those before the therapeutic period, ΣST segment depression decreased and treadmill walking time increased significantly in group B but not in group A after the therapeutic period. These findings suggest that less frequent doses of isosorbide dinitrate may prevent development of nitrate tolerance, which is confirmed by vascular ultrasonography combined with treadmill exercise in patients with coronary heart disease.